Sensitive Subject

Online tests claim they can identify the foods behind your complexion and health woes—and provide a solution. Are they worth it? Ahead, experts weigh in and offer sound strategies for a face-first eating plan.

- April Benshosan

You know her—that friend who swore off sugar and insists her skin has never looked better. You may roll your eyes and reach for a tube of retinol, but don’t write her off so quickly: What you put in your mouth can show up on your face, according to research, and it’s fueling a proliferation of health sites and med spas offering food “sensitivity” tests and personalized diet plans that pledge to leave your skin smooth and blemish-free.

These tests rely on a small blood sample, sometimes self-collected, that companies claim can be used to assess your reactivity to certain foods, leaving you with a laundry list of items to slash from your eating routine. The promise: Banishing them from your Instacart can transform your complexion. After all, a tiny skin prick is a small price to pay for clearer skin, right?

We spoke to experts to get the truth about how food intolerances and allergies—as well as your diet in general—affect your complexion, and whether these tests are legit. Their answers might save you some blood (and maybe some sweat and tears too).

Food for Thought

LET'S START WITH WHAT WE KNOW FOR SURE: In some cases, what you consume does have an immediate and measurable impact on the state of your skin. Take a true food allergy, for example. "When you ingest something you're allergic to, the immune system recognizes the offender as something foreign because your body has developed immunoglobulin E [IgE] antibodies against it," says Purvi Parikh, MD, an allergist with the Allergy & Asthma Network.